/Engine/Source/Runtime/GeometryCore/Public/DynamicMesh/MeshNormals.h
Compute normal at mesh vertex by weighted sum of one-ring triangle normals. Can optionally weight by area, angle, or both (averaged)
the vertex normal at vertex VertIdx of Mesh.
static FVector3d ComputeVertexNormal ( const [FDynamicMesh3](API\Runtime\GeometryCore\DynamicMesh\FDynamicMesh3) & Mesh, int VertIdx, bool bWeightByArea, bool bWeightByAngle )